1. Field of the Invention
This invention relates to an endoscope-covering sheath used for endoscopic blood vessel harvesting which endoscopically harvests a subcutaneous blood vessel such as a great saphenous vein.
2. Description of the Related Art
A cannula and a surgical method that are used for endoscopically pulling and harvesting a subcutaneous blood vessel such as a great saphenous vein are known in, for example, PCT/US99/31242 and Laid-Open Japanese Patent Application No. 2000-37,389.
The cannula is a straight tubular device having an instrument inserting passage in its inside, and a manipulating portion is provided at the proximal end of the cannula. A traction device, a rigid endoscope and dissecting forceps are removably inserted in the instrument inserting passage of the cannula from the end of the manipulating portion. The traction device has at its distal end a loop portion that projects from the tip of the cannula and makes an angle with the axial direction of the cannula.
When a subcutaneous blood vessel, such as a great saphenous vein, is to be endoscopically harvested by using the cannula, the following surgical method is adopted. Namely, referring to FIG. 23, when an operator is to harvest the entire length of a harvesting target blood vessel (hereinafter referred to as a blood vessel) C such as a great saphenous vein which extends from the upper portion of the inguinal region A of the thigh of a lower limb 1000 to an ankle B, the operator dissects, for example, A portion of skin E1, E2 or E3 at the upper portion of the inguinal region A, the knee D and the ankle B respectively immediately above the blood vessel C by means of a scalpel or the like.
The operator exposes the blood vessel C in the area of the dissected portion of skin E1, E2 or E3 by means of a dissector 3 or the like. Further, the operator parts tissue immediately above the blood vessel C by means of the same or similar dissector over a distance from the dissected portion of skin E1, E2 or E3, such that the blood vessel is observable with the naked eyes.
FIG. 24 is a cross-sectional view taken along line 24—24 of FIG. 23. Reference numeral 1001 denotes skin, reference numeral 1002 denotes a subcutaneous tissue, and reference numeral 1003 denotes a connective tissue of the blood vessel. The blood vessel C exists under the connective tissue 1003 of the blood vessel. First of all, the operator uses as a dissector a cannula having a conical tip secured to its cannula tip and forms a cavity G from the surrounding tissue to separate it from the blood vessel C. In the following description, reference will be made to the harvesting of the blood vessel C which extends between the dissected portion of skin E2 of the knee D and the inguinal region A. The operator removes the conical tip from the tip of the cannula, and inserts the cannula into the cavity G through the dissected portion of skin E2 and inserts the cannula toward the dissected portion of skin E1 of the knee D along the top portion of the blood vessel C while observing through a rigid endoscope.
In the course of inserting the cannula into the cavity G, while the operator is repeatedly moving the traction device back and forth by manipulating a manipulating portion disposed at the proximal end of the cannula, the operator holds the blood vessel C with the loop portion disposed at the distal end of the cannula and separates from the blood vessel C the subcutaneous tissue 1002 and the connective tissue of blood vessel 1003, and cuts a plurality of side branch vessels F which branch off from an intermediate portion of the blood vessel C, with the dissecting forceps. The operator repeats this manipulation to harvest the blood vessel C extending between the dissected portion of skin E2 and the inguinal region A.
When the cannula is forced into the cavity G, adhering matter such as blood, mucosa and subcutaneous fat existing in the cavity adheres to the objective lens surface of the endoscope and hinders the viewing field of the endoscope. In addition, the cannula has a structure in which the traction portion and the dissecting forceps are removably inserted through the sheath, and the operator performs manipulation with the traction device and the dissecting forceps projected from the sheath.
Accordingly, after adhering matter such as blood, mucosa and subcutaneous fat existing in the cavity adheres to the traction device and the dissecting forceps, when the traction portion and the dissecting forceps are retracted into the sheath, adhering matter such as blood, mucosa and subcutaneous fat adheres to the objective lens surface of the endoscope and hinders the viewing field of the endoscope.
For this reason, in the related art, when the viewing field of the endoscope is hindered, the operator temporarily stops operations, pulls the endoscope out of the sheath, and wipes the objective lens surface, and again inserts the endoscope into the sheath. However, this leads to the problem that operation time is prolonged.
To solve this problem, it is known that as disclosed in Laid-Open Japanese Patent Application No. Hei 8-29,699, a wiper for wiping an objective lens surface is provided on the end surface of the casing of an objective lens in an endoscope and the wiper is driven by a motor provided in the interior of the casing of the objective lens.
In addition, as disclosed in Laid-open Japanese utility Model Application No. Sho 62-176,817, it is know that in an endoscope of the type in which an observation window and an illuminating window are arranged adjacently in the axial direction in the tip portion (along the length) of the endoscope, a wiper is constructed to move axially back and forth along the tip portion of the endoscope to wipe the observation window and the illuminating window.
However, the former endoscope is constructed to drive the wiper by electric power, and needs a complicated structure and an increased cost. The former endoscope also has the problem that since a motor is contained in the casing of the objective lens, the tip of the endoscope is large in diameter. The latter endoscope has a structure that allows the wiper to move axially back and forth along the tip portion of the endoscope by a handle being rotated back and forth by an operator-side manipulating portion, that is, a structure that transforms rectilinear motion into rotary motion, so that speedy manipulation is impossible. In addition, the driving system is complicated and entails a cost increase.